The present invention relates to a data transmission system, a header-information adding device, a data-format converting device, and a data transmission method. More particularly, the present invention relates to a data transmission system, a header-information adding device, a data-format converting device, and a data transmission method for nodes connected to a network.
It has become more and more common to transmit applications having audio/visual (A/V) information, including moving pictures and still images, over a network. Sometimes the transmission of these applications is done commercially.
Since a broadband network is required to transmit such applications having A/V information, typically, information compression techniques such as JPEG (Joint Photographic Experts Group), MPEG (Moving Picture Experts Group), and ATRAC (Adaptive Transform Acoustic Coding) have been used for high-quality moving image data transmission.
Compression techniques such as JPEG, MPEG, and ATRAC often use a unique compression format, and are generally not compatible with one another. Thus, an encoder at a sending node and a decoder at a receiving node must employ the same data format to transmit such multimedia information over a network. Without compatibility, data sent from the sending node cannot be handled as active data by the receiving node, and therefore the receiving node cannot recognize the data sent from the sending node.
A data transmission system and method capable of successfully exchanging data between a sending node and a receiving node in which the data formats are incompatible with each other, is disclosed in Japanese Unexamined Patent Application Publication No. 10-271146. In this system and method, an intermediate node for converting the data format is provided between the data sending and receiving nodes, and converts the sending-node data format so that the data from the sending node can be handled as active data by the receiving node.
In the data transmission system and method disclosed in the above cited reference, however, the intermediate node must know the data formats that can be handled by the sending node and the receiving node in advance. Therefore, a problem with this system and method is that the sending node and the receiving node must comply with a special protocol by which the intermediate node specifies the data format at the sending node and at the receiving node.